1. Field of the Invention
The invention relates to an alternating load stable, switchable semiconductor element where the pre-treated edge zone of the semiconductor wafer is disposed between two annular insulating bodies and covered with a surface stabilizing material and where the current conductor for the control electrode of the semiconductor wafer is led through one of the insulating bodies.
2. Brief Description of the Background of the Invention Including Prior Art
Semiconductor devices with high loadability of current are subjected to an extreme loading by push, thrust and shearing forces upon use under alternating load due to the generated extreme loading corresponding to the change in the operating temperature and in particular at the connection surfaces of adjoining materials with different thermal expansion coefficients. Soft solder contacts, as they are employed between the semiconducting material and the adjoining contact pieces in semiconductor device elements of small power and for constant load, are not stable because of the resulting embrittling of the contact surfaces, the so-called contact aging, caused by the extreme loading. In addition, steps for improving such tin solder materials have not in all cases produced the desired alternating load stability of the soldering contacts.
It is known to employ hard solder junctions in the case of semiconductor rectifier elements for such an extreme loading. The high cost of the process and the frequently observed interference with the properties of the semiconductor materials due to the high processing temperatures are particular disadvantages of such constructions.
A solution of the problem was achieved with the so-called pressure contacting. The advantages of this technique as compared to the soldering contact method are that no contact aging occurs, that under certain conditions mechanical tensions are balanced by sliding of adjoining materials, that the contact layers can be tested in a destruction free manner and that the expense of the process is substantially less.
In comparison, soldering contacts exhibit the advantage of lower thermal resistance and thus better thermal and also electrical operating behavior as well as a higher loadability with peak currents. In particular, these properties have substantial importance in the operation of semiconductor devices subject to alternating loads.
Presently, semiconductor devices in addition are employed in the shape of discrete individual elements as semiconductor construction units in compact construction with at least two electrically switched elements, that is, in so-called power modules, for loading with alternating power loads. These power modules are associated with the advantage of favorable cost of the construction and are associated with a simple electrical contacting of the device parts. For economic reasons, the exchangeability of the semiconductor device elements and of their contact construction components is desired at all steps of the assembling. This forces the provision of pressure contacting of the device elements.
Power modules are known where the semiconductor device elements are in fact pressure contacted, however they are embedded in a cast resin including a section of the joining contact components. This construction renders ineffective the advantages of pressure contacting.
According to other modular constructions, the semiconductor device elements are formed by stacking of contact and envelope bodies with the semiconductor wafer as well as by employing sealing materials. These constructions do not exhibit in all cases the desired long-term stability.
Finally, power modules are known which included discrete, disk-shaped semiconductor devices based on a substantially more costly construction.
It is common to the known semiconductor devices and construction units that their semiconductor device elements or parts of them are employable only in the specific construction form based on their specific design or the construction form desired in each case. The limited possibilities of application of such semiconductor device elements in addition require an expensive maintenance of storage of device components.